Stuck in California: Shuttle Endeavour’s Delayed Flight Home

Endeavour successfully took off atop a 747 this morning under blue skies. Farewell Endeavour, it was a joy to have you visit (NASA)

[/caption]

Update: Space Shuttle Endeavour left Edwards Air Force Base this morning at 7am, after a 10-day stop over in the Mojave Desert, 65 miles northeast of Los Angeles. Have a safe flight to Florida Endeavour, it was great to have you as a guest!

You’ve probably heard this announcement at the airport before: “Flight delayed due to bad weather.” Quickly followed by, “You can’t be serious!” from the red-faced guy behind you, slamming his briefcase to the floor, resulting in an angry hoard of commuters rushing to the ticket desk to blame the airline for the snow storm outside (because the natural phenomenon of snow is their fault).

However, at Edwards Air Force Base in California, another, more patient passenger awaits her flight back to Florida. But rather than the delay being a matter of minutes or hours, Space Shuttle Endeavour’s flight to Florida has been delayed by three days, and counting…

Endeavour had an astounding mission (STS-126) to the International Space Station last month. The shuttle carried a team of seven to perform one of the busiest 16-day orbital stop-overs yet. The crew completed several spacewalks to fix stiff solar alpha rotary joints, upgraded the station modules to accommodate six permanent station crew members and transported some cool educational experiments into space.

"I just heard some sort of explosion!" Nope, it was just that pesky space shuttle... (LA Times)
"I just heard some sort of explosion!" Nope, it was just that pesky space shuttle... (LA Times)
All in all, STS-126 was an outright success. Even the confused spiders in the biology experiment payload performed with excellence, dealing with microgravity and spinning a web just like they did on Earth. Everything appeared to go pretty much without incident (apart from the loss of a $100,000 toolbag), that was until Endeavour was told to land 2000 miles off target due to bad weather over Florida. Rather than returning to home soil, the shuttle landed at Edwards Air Force Base in the Mojave Desert in California (buzzing the locals on November 30th).

So alternative arrangements had to be made to ferry the shuttle back to Kennedy Space Center, and this included a customized NASA Boeing 747 jumbo jet taxi ride (with a fare of $1.8 million). Endeavour will enjoy a piggyback ride atop the aircraft, hopefully taking off first thing in the morning (Wednesday).

NASA is keeping a close eye on the weather front causing the problems; Endeavour was tentatively scheduled to fly home on Sunday, but poor weather between California and Florida pushed the delay further into the week. NASA does not allow the flying duo to pass through cloud or any inclement weather, so they are allowed to be picky about when to fly.

Sources: Space.com, LA Times, Florida Today

Beyond Any Reasonable Doubt: A Supermassive Black Hole Lives in Centre of Our Galaxy

The stars in the centre of our galaxy. Our supermassive black hole IS in there, somewhere... (ESO)

[/caption]

One the one hand, this might not be surprising news, but on the other, the implications are startling. A supermassive black hole (called Sagittarius A*) lives at the centre of the Milky Way. This is the conclusion of a 16 year observation campaign of a region right in the centre of our galaxy where 28 stars have been tracked, orbiting a common, invisible point.

Usually these stars would be obscured by the gas and dust in that region, but the European Southern Observatory (ESO) in Chile has used its infrared telescopes to peer deep into the black hole’s lair. Judging by the orbital trajectories of these 28 stars, astronomers have not only been able to pinpoint the black hole’s location, they have also deduced its mass…

It has been long recognised that supermassive black holes probably occupy the centres of most galaxies, from dwarf galaxies to thin galactic disks to large spiral galaxies; the majority of galaxies appear to have them. But actually seeing a black hole is no easy task; astronomers depend on observing the effect a supermassive black hole has on the surrounding gas, dust and stars rather than seeing the object itself (after all, by definition, a black hole is black).

Yearly location of stars within 0.2 parsecs from Sagittarius A* orbiting the common, compact radio source (from a different research paper by A. Ghez)In 1992, astronomers using the ESO’s 3.5-metre New Technology Telescope in Chile turned their attentions on our very own galactic core to begin an unprecedented observation campaign. Since 2002, the 8.2-metre Very Large Telescope (VLT) was also put to use. 16 years later, with over 50 nights of total observation time, the results are in.

By tracking individual stars orbiting a common point, ESO researchers have derived the best empirical evidence yet for the existence of a 4 million solar mass black hole. All the stars are moving rapidly, one star even completed a full orbit within those 16 years, allowing astronomers to indirectly study the mysterious beast driving our galaxy.

The centre of the Galaxy is a unique laboratory where we can study the fundamental processes of strong gravity, stellar dynamics and star formation that are of great relevance to all other galactic nuclei, with a level of detail that will never be possible beyond our Galaxy,” explains Reinhard Genzel, team leader of this research at the Max-Planck-Institute for Extraterrestrial Physics in Garching near Munich, Germany.

Undoubtedly the most spectacular aspect of our 16-year study, is that it has delivered what is now considered to be the best empirical evidence that super-massive black holes do really exist,” Genzel continues. “The stellar orbits in the galactic centre show that the central mass concentration of four million solar masses must be a black hole, beyond any reasonable doubt.”

Apart from being the most detailed study of Sagittarius A*’s neighbourhood (the techniques used in this study are six-times more precise than any study before it), the ESO astronomers also deduced the most precise measurement of the distance from the galactic centre to the Solar System; our supermassive black hole lies a safe 27,000 light years away.

A lot of information was gleaned about the individual stars too. “The stars in the innermost region are in random orbits, like a swarm of bees,” says Stefan Gillessen, first author of the paper published in The Astrophysical Journal. “However, further out, six of the 28 stars orbit the black hole in a disc. In this respect the new study has also confirmed explicitly earlier work in which the disc had been found, but only in a statistical sense. Ordered motion outside the central light-month, randomly oriented orbits inside – that’s how the dynamics of the young stars in the Galactic Centre are best described.”

Quite simply, the object influencing these stars must be a supermassive black hole, there is no other explanation out there. Does this mean black holes have an even firmer standing as a cosmological “fact” rather than “theory”? It would appear so

Sources: ESO, BBC

Life on Mercury

How hot is it on Mercury? Color image of Mercury. Image credit: NASA

[/caption]
Mercurian world is one of extremes. 700 Kelvin on the side exposed to the Sun, yet some areas are never exposed to sunlight and are as cold as deep space. Scientists do not believe there has ever been life on Mercury. The atmosphere on Mercury is almost non-existant. It doesn’t protect the planet from the harsh radiation of the Sun or radiation from space, nor does it trap heat and provide a breathable atmosphere. Mercury is inhospitable and sterile.

In order for life (as we know it) to exist, Mercury would need to have temperatures that allow liquid water to remain on its surface for long periods of time. But the temperatures on Mercury extend from just above absolute zero when the surface is shadowed to 700 Kelvin when its in sunlight. Liquid water just can’t exist in that kind of environment.

Any ancient life on Mercury would have faced many extinction events. Here on Earth many past life forms have been destroyed by asteroid impacts. The dinosaurs are a classic example. Images of Mercury’s surface returned by the Mariner 10 and MESSENGER spacecraft have shown that the surface has suffered many large impacts. In fact, it was heavily bombarded during the Late Heavy Bombardment that occurred about 3.9 billion years ago. Any one of those impacts could have destroyed any life on the planet. Many scientists believe that a great deal of the planet’s surface was stripped away by one impact. If the impact removed a large portion of the surface, surely it would have taken any life that existed at the time with it.

All evidence that science has do date indicates that there has never been life on Mercury and never will be. The harsh conditions on the planet’s surface and the tenuous atmosphere make it impossible for any life form known to man to exist.

But there are other planets in the Solar System. Here’s an article about life on Pluto, and here’s one about life on Mars.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Vida sobre el mercurio

References:
NASA Solar System Exploration: Mercury
Wikipedia
JAXA: Mercury Quantities
NASA MESSENGER Mission
NASA Multimedia

Carbon Dioxide Detected on Exoplanet HD 189733b

Artist's impression of a transiting exoplanet (ESA - C.Carreau)

[/caption]The Hubble Space Telescope has detected carbon dioxide on a planet orbiting another star. The star in question is HD 189733 (also known as V452 Vulpeculae, a variable star designation), a binary system over 60 light years away, and the planet is approximately the size of Jupiter (called HD 189733b). The exoplanet is already known to contain water and methane molecules from previous Hubble and Spitzer campaigns, but this is the first time CO2 has been discovered.

But why all the fuss? CO2 is another chemical marker for the existance of life. But HD 189733b isn’t a candidate planet for the search for life. After all, this “hot Jupiter” will not be hospitable to the development of even the most basic lifeforms (life as we know it in any case). This discovery is ground-breaking in that CO2 can be sensed on a planet many light years from Earth…

The carbon dioxide is kind of the main focus of the excitement, because that is a molecule that under the right circumstances could have a connection to biological activity as it does on Earth,” said Mark Swain of NASA’s Jet Propulsion Laboratory. “The very fact that we’re able to detect it, and estimate its abundance, is significant for the long-term effort of characterizing planets both to find out what they’re made of and to find out if they could be a possible host for life.”

Indeed, it wasn’t only carbon dioxide that was found; carbon monoxide was also detected in the exoplanet’s atmosphere. But the fact that CO2 is a “tracer” for life and it has been detected on a planet other than a planet known to contain life (Earth) is incredibly significant. As time goes on, observation techniques advance, it is hoped small rocky bodies will be observed. If this can be done, an Earth-like planetary survey can be carried out.

Earth atmospheric molecules detected by Venus Express (ESA)
Earth atmospheric molecules detected by Venus Express (ESA)
In fact, ESA’s Venus Express was recently used to characterize what Earth looks like from a distant vantage point, providing astronomers and future extraterrestrial hunters with a model that can be used when observing distant star systems. If a planet, with a similar chemical composition to that of the Earth is discovered, it would become a prime candidate for harbouring alien life.

So how did Hubble detect CO2 on HD 189733b? Through a spectroscopic analysis of the infrared radiation being emitted by the hot planet, Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) spotted an abundance of CO and CO2. Certain molecules in the exoplanet’s atmosphere absorb certain wavelengths of infrared light, leaving a spectroscopic “fingerprint” in the light detected by Hubble.

This kind of campaign is best carried out on star systems with their ecliptic plane seen edge-on to the Earth. This means the orbit of the exoplanet carries it behind the parent star and then infront of it. HD 189733b transits (or eclipses) its parent star every 2.2 days and then orbits behind the star. This is an ideal situation as astronomers are able to measure the emission from the star (when the line of sight to the exoplanet is blocked by the star) and use those measurements to subtract from spectroscopic analysis of the exoplanet. This technique isolates the exoplanet emission making it possible to analyse the chemical composition of its “day-side” atmosphere.

We’re starting to find the molecules and to figure out how many of them there are to see the changes between the day side and the night side,” Swain said.

All these developments by Hubble will aid the future of exoplanet studies. In 2013, NASA’s James Webb Space Telescope will be launched to look out for “super-Earth” exoplanets (i.e. rocky planets larger than Earth), observing in near-infrared wavelengths. Therefore, the carbon dioxide discovery in the atmosphere of HD 189733b helps astronomers refine techniques to detect yet another tracer for life…

Source: HubbleSite

Pluto and Neptune

Neptune from Voyager 2. Image credit: NASA/JPL

[/caption]
The most distant planet in the Solar System is Neptune, orbiting at a distance of 4.5 billion km from the Sun. But there used to be 9 planets in the Solar System, including Pluto. And for most of the time since its discovery, Pluto was considered the most distant planet from the Sun.

Pluto and Neptune couldn’t be more different. Pluto is a tiny Kuiper Belt Object; a ball of rock and ice measuring only 2,390 km across. This is a tiny fraction of the diameter of Neptune, which is 49,500 km across. You could fit 20 Plutos side by side to match the diameter of Neptune.

Neptune and Pluto have a very interesting orbital dynamic between them. Neptune has a roughly circular orbit; however, Pluto’s orbit is highly eccentric, varying its distance to the Sun a tremendous amount over the course of its orbit. Because of this, Pluto can actually get closer to the Sun than Neptune. The last time this happened started in 1979 and went until 1999. During that period, Neptune was actually the most distant planet from the Sun, and Pluto was actually closer. But then Pluto was demoted, from planet to dwarf planet, so Neptune is now the most distant planet; and it doesn’t matter what Pluto does. Pluto spends 20 years out of its entire 248 year orbit within Neptune’s orbit.

Since Pluto and Neptune cross orbits, is it possible that the two planets will collide? No, they actually can’t collide because Pluto’s orbit takes it much higher above the Sun’s orbital plane. When Pluto is at the same point as Neptune’s orbit, it actually much higher up than Neptune. So the two planets will never be at the same place at the same time.

You can read some interesting information about the orbital patterns of Pluto here.

We have written many articles about Pluto and Neptune on Universe Today. Here’s why Pluto is no longer considered a planet, and here’s an article about how there could be liquid oceans inside Neptune.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.

Source: NASA

What is the Weather Like on Neptune?

Reconstruction of Voyager 2 images showing the Great Black spot (top left), Scooter (middle), and the Small Black Spot (lower right). Credit: NASA/JPL

Neptune is the most distant planet from the Sun, with temperatures that plunge down to 55 Kelvin, or -218 degrees Celsius. You would think that a planet that cold would be frozen and locked down, with very little weather. But you’d be very wrong. In fact, the weather on Neptune is some of the most violent weather in the Solar System.

Just like Jupiter and Saturn, Neptune has bands of storms that circle the planet. While the wind speeds on Jupiter can reach 550 km/hour – twice the speed of powerful hurricanes on Earth, that’s nothing compared to Neptune. Astronomers have clocked winds on Neptune traveling at 2,100 km/hour.

So why can the winds on Neptune reach such huge speeds? Astronomers think that the cold temperatures on Neptune might have something to do with that after all. The cold temperatures might decrease the friction in the system, so that winds can get going fast on Neptune.

During its 1989 flyby, NASA’s Voyager 2 spacecraft discovered the Great Dark Spot on Neptune. Similar to Jupiter’s Great Red Spot, this is an anti-cyclonic storm measuring 13,000 km x 6,600 km across. A few years later, however, the Hubble Space Telescope failed to see the Great Dark Spot, but it did see different storms. This might mean that storms on Neptune don’t last as long as they do on Jupiter or even Saturn.

The more active weather on Neptune might be due, in part, to its higher internal heat. Although Neptune is much more distant than Uranus from the Sun, receiving 40% less sunlight, temperatures on the surface of the two planets are roughly similar. In fact, Neptune radiates 2.61 times as much energy as it receives from the Sun. This is enough heat to help drive the fastest winds in the Solar System.

We have written many articles about Neptune for Universe Today. Here’s an article about how Neptune’s south pole is the warmest part of the planet, and here’s more information about the atmosphere on Neptune.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.

Neptune Compared to Earth

Neptune compared to Earth. Image credit: NASA

[/caption]
To really understand how big Neptune really is, you need some kind of comparison. Let’s see how Neptune compares to Earth in every way.

First, let’s just look at pure size. The diameter of Neptune is approximately 49,500 km. This makes Neptune the 4th largest planet in the Solar System. And compared to Earth? Neptune is 3.9 times bigger.

Now mass. The mass of Neptune is 1.02 x 1026 kg. If you wanted to write it out, it would be 102,000,000,000,000,000,000,000,000 kg. Neptune has 17 times as much mass compared to the Earth.

How about volume? The volume of Neptune is 6.3 x 1013 km3. You could fit 57 Earths inside Neptune and still have room to spare.

A day on Earth is 24 hours, but a day on Neptune is 16 hours and 6 minutes. A year on Earth is, um, 1 year obviously, while a year on Neptune is 164.79 years.

Here’s one element that’s actually pretty close. The surface gravity on Neptune (if it actually had a surface that you could stand on) is only 14% stronger than the pull of gravity on Earth. You would have a difficult time noticing if you were standing on the surface of Neptune compared to the surface of Earth.

We have written many articles about Neptune for Universe Today. Here’s an article about three new trojan asteroids found in Neptune’s orbit, and a possible mission to Neptune under study.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.

Neptune’s Orbit

Neptune seen from Earth. Image credit: Keck

[/caption]
Neptune orbits the Sun at an average distance of 4.5 billion km.

That’s the simple answer to the question, what is the orbit of Neptune. However, things are actually a little more complicated than that. Like all the planets in the Solar System, Neptune follows an elliptical path around the Sun, varying its distance to the Sun at different points along its orbit.

At its closest point in its orbit, which astronomers call perihelion, Neptune gets within 4.45 billion km, or 29.77 astronomical units (1 astronomical unit or AU is the average distance of the Earth to the Sun).

At its most distant point in its orbit, called aphelion, Neptune reaches a distance of 4.55 billion km, or 30.44 astronomical units.

One interesting feature about the orbit of Neptune is the fact that Pluto’s very elliptical orbit sometimes brings it closer to the Sun. Back in the days when Pluto was still a planet, it would spend a few decades every orbit closer to the Sun. So Neptune was actually the most distant planet, and Pluto was closer. The last time this happened started in 1979, and ended in 1999. Of course, Pluto isn’t a planet any more, so Neptune’s orbit makes it the most distant planet.

We have written many article about Neptune on Universe Today. Here’s an article with images of Neptune captured by the Hubble Space Telescope. And here’s another discussing the planet’s relatively warm south pole.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.

Radius of Neptune

Neptune compared to Earth. Image credit: NASA

[/caption]
The equatorial radius of Neptune is 24,764 km.

That’s the quick answer. But you need to understand that things are a little more complicated. Like all of the planets in the Solar System, Neptune is spinning rapidly, completing a rotation in 16 hours and 6 minutes. This rapid rotation causes the planet to flatten out, so that the radius across the equator is bigger than the radius to the poles.

So here’s the more precise answer. The radius of Neptune, measured from the center to the equator is 24,764 km. And the radius of Neptune, measured from the center to either pole is 24,341 km. I’ll do the math for you. That means that the points on the equator are 423 km further away from the center of Neptune than either pole.

Need some comparison? Neptune’s radius is 3.9 times the radius of Earth. In other words, you could line up almost 4 Earths side by side to match the width of Neptune.

We have written many articles about Neptune for Universe Today. Here’s an article about the potential for liquid water deep down within Neptune. And here’s an article about how Neptune’s largest moon Triton might have been captured by Neptune’s gravity.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.

Size of Neptune

Neptune compared to Earth. Image credit: NASA

[/caption]
Neptune is so dim and distant that you can only see it with a moderately powerful telescope. But Neptune is the 4th largest planet in the Solar System. Let’s take a look at how big Neptune is, and compare it to some other objects that you might be familiar with.

Neptune is the 4th largest planet in the Solar System, after Jupiter, Saturn, and Uranus. It’s much larger than the terrestrial planets: Mercury, Venus, Earth and Mars.

The diameter of Neptune is 49,500 km. Need some comparison? That’s approximately 3.9 times the diameter of Earth. In other words, you could put almost 4 Earths side to side to match the diameter of Neptune.

The volume of Neptune is 6.25 x 1013 km3. That’s an enormous number, so once again, for comparison, that’s 57.7 times the volume of Earth. You could fit 57 Earths inside Neptune with room to spare.

The surface area of Neptune is 7.64 x 109 km2. That’s 15 times as much surface area as Earth; of course, Neptune doesn’t have a solid surface, so you wouldn’t want to live there.

The mass of Neptune is 1.02 x 1026 kg. Again, for comparison, that’s the equivalent of 17.1 Earths.

So now, when you look through a telescope and see that tiny blue-green dot, you can get a better sense of the size of Neptune.

We have written many articles about Neptune on Universe Today. Here’s an article about a minor planet found near Neptune. And an article about how Neptune’s south pole is the hottest place on the planet.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.