Universe Today

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All you galactic hitchhikers take note: a new atlas of the inner regions of the Milky Way was released today, showing thousands of previously undiscovered dense knots of cold cosmic dust — the potential birthplaces of new stars. This new map of the home galaxy was made using observations from the APEX telescope in Chile, showing the Milky Way in submillitere wavelengths. “ATLASGAL gives us a new look at the Milky Way. Not only will it help us investigate how massive stars form, but it will also give us an overview of the larger-scale structure of our galaxy”, said Frederic Schuller from the Max Planck Institute for Radio Astronomy, leader of the ATLASGAL team.

So, grab your towels and let’s head out!

This is the largest map available of cold dust, and astronomers say it will provide an invaluable map for observations made with the forthcoming ALMA telescope, as well as the recently launched ESA Herschel space telescope.

The area of the new submillimeter map is approximately 95 square degrees, covering a very long and narrow strip along the galactic plane two degrees wide (four times the width of the full Moon) and over 40 degrees long. The 16,000 pixel-long map was made with the LABOCA submillimeter-wave camera on the ESO-operated APEX telescope. APEX is located at an altitude of 5100 m on the arid plateau of Chajnantor in the Chilean Andes — a site that allows optimal viewing in the submillimeter range. The Universe is relatively unexplored at submillimeter wavelengths, as extremely dry atmospheric conditions and advanced detector technology are required for such observations.

And click here to see an annotated pan of part of the galactic plane.

Highlights of the map include the center of the Milky Way, the nearby massive and dense cloud of molecular gas called Sagittarius B2, and a bubble of expanding gas called RCW120, where the interstellar medium around the bubble is collapsing and forming new stars.

“It’s exciting to get our first look at ATLASGAL, and we will be increasing the size of the map over the next year to cover all of the galactic plane visible from the APEX site on Chajnantor, as well as combining it with infrared observations to be made by the ESA Herschel Space Observatory. We look forward to new discoveries made with these maps, which will also serve as a guide for future observations with ALMA”, said Leonardo Testi from ESO, who is a member of the ATLASGAL team and the European Project Scientist for the ALMA project.

The interstellar medium — the material between the stars — is composed of gas and grains of cosmic dust, rather like fine sand or soot. However, the gas is mostly hydrogen and relatively difficult to detect, so astronomers often search for these dense regions by looking for the faint heat glow of the cosmic dust grains.
Submillimetre light allows astronomers to see these dust clouds shining, even though they obscure our view of the Universe at visible light wavelengths.

The newly released map also reveals thousands of dense dust clumps, many never seen before, which mark the future birthplaces of massive stars. The clumps are typically a couple of light-years in size, and have masses of between ten and a few thousand times the mass of our Sun. In addition, ATLASGAL has captured images of beautiful filamentary structures and bubbles in the interstellar medium, blown by supernovae and the winds of bright stars.

Source: ESO

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Let’s compare and contrast the two most different planets in the Solar System, Mercury and Jupiter. Of course, you probably know that Mercury is the smallest planet in the Solar System while Jupiter is the largest planet in the Solar System.

First, let’s just take a look at the physical measurements of Jupiter and Mercury. The diameter of Mercury is 4,879.4 km, while the diameter of Jupiter is 142,984 km. In other words, Jupiter is 29.3 times bigger across than Mercury. In terms of volume, you could fit 24,462 Mercurys inside Jupiter. Jupiter even has 5,750 times more mass than Mercury.

Now let’s take a look at their composition. Mercury is a rocky terrestrial planet, with a high density. In fact, the liquid iron core of Mercury accounts for 42% of the planet, and this is surrounded by a mantle and crust of silica. Jupiter in comparison is a relatively less dense gas giant planet; it’s made up almost entirely of hydrogen and helium, with a few other trace elements.

Mercury orbits very close to the Sun, with an average orbital distance of 57.9 million kilometers. Because it orbits so close, Mercury completes an orbit around the Sun every 88 days. Jupiter, on the other hand, is located 778.5 million km from the Sun and takes 11.86 years to complete a single year.

Mercury has no moons or rings, while Jupiter has a faint set of rings and 63 named natural satellites so far.

It sounds like Jupiter and Mercury are different in every way, but there’s one big similarity. You can see them both with your own eyes. Jupiter is very bright and often very high in the sky. In fact, if you see a really bright star in the sky in the middle of the night, you’re probably seeing Jupiter, and not a star at all. Mercury is also possible to see with your own eyes. But since Mercury orbits so close to the Sun, you’ll only see it shortly after sunset or before sunrise until the Sun washes out the night sky.

We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed.

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.

Mercurio y Júpiter

Reference:
NASA