What are Quark Stars?

We’ve covered the full range of exotic star-type objects in the Universe. Like Pokemon Go, we’ve collected them all. Okay fine, I’m still looking for a Tauros, and so I’ll continue to wander the streets, like a zombie staring at his phone.

Now, according to my attorney, I’ve fulfilled the requirements for shamelessly jumping on a viral bandwagon by mentioning Pokemon Go and loosely connecting it to whatever completely unrelated topic I was working on.

Any further Pokemon Go references would just be shameless attempts to coopt traffic to my channel, and I’m better than that.

It was pretty convenient, though, and it was easy enough to edit out the references to Quark on Deep Space 9 and replace them with Pokemon Go. Of course, there is a new Star Trek movie out, so maybe I miscalculated.

Anyway, now that we got that out of the way. Back to rare and exotic stellar objects.

The white dwarf G29-38 (NASA)
The white dwarf G29-38. Credit: NASA

There are the white dwarfs, the remnants of stars like our Sun which have passed through the main sequence phase, and now they’re cooling down.

There are the neutron stars and pulsars formed in a moment when stars much more massive than our Sun die in a supernova explosion. Their gravity and density is so great that all the protons and electrons from all the atoms are mashed together. A single teaspoon of neutron star weighs 10 million tons.

And there are the black holes. These form from even more massive supernova explosions, and the gravity and density is so strong they overcome the forces holding atoms themselves together.

White dwarfs, neutron stars and black holes. These were all theorized by physicists, and have all been discovered by observational astronomers. We know they’re out there.

Is that it? Is that all the exotic forms that stars can take?  That we know of, yes, however, there are a few even more exotic objects which are still just theoretical. These are the quark stars. But what are they?

Artist concept of a neutron star. Credit: NASA
Artist concept of a neutron star. Credit: NASA

Let’s go back to the concept of a neutron star. According to the theories, neutron stars have such intense gravity they crush protons and electrons together into neutrons. The whole star is made of neutrons, inside and out. If you add more mass to the neutron star, you cross this line where it’s too much mass to hold even the neutrons together, and the whole thing collapses into a black hole.

A star like our Sun has layers. The outer convective zone, then the radiative zone, and then the core down in the center, where all the fusion takes place.

Could a neutron star have layers? What’s at the core of the neutron star, compared to the surface?

The idea is that a quark star is an intermediate stage in between neutron stars and black holes. It has too much mass at its core for the neutrons to hold their atomness. But not enough to fully collapse into a black hole.

The difference between a neutron star and a quark star (Chandra)
The difference between a neutron star and a quark star. Credit: Chandra

In these objects, the underlying quarks that form the neutrons are further compressed. “Up” and “down” quarks are squeezed together into “strange” quarks. Since it’s made up of “strange” quarks, physicists call this “strange matter”. Neutron stars are plenty strange, so don’t give it any additional emotional weight just because it’s called strange matter. If they happened to merge into “charm” quarks, then it would be called “charm matter”, and I’d be making Alyssa Milano references.

And like I said, these are still theoretical, but there is some evidence that they might be out there. Astronomers have discovered a class of supernova that give off about 100 times the energy of a regular supernova explosion. Although they could just be mega supernovae, there’s another intriguing possibility.

They might be heavy, unstable neutron stars that exploded a second time, perhaps feeding from a binary companion star. As they hit some limit, they converting from a regular neutron star to one made of strange quarks.

But if quark stars are real, they’re very small. While a regular neutron star is 25 km across, a quark star would only be 16 km across, and this is right at the edge of becoming a black hole.

A neutron star (~25km across) next to a quark star (~16km across). Original Image Credit: NASA's Goddard Space Flight Center
A neutron star (~25km across) next to a quark star (~16km across). Original Image Credit: NASA’s Goddard Space Flight Center

If quark stars do exist, they probably don’t last long. It’s an intermediate step between a neutron star, and the final black hole configuration. A last gasp of a star as its event horizon forms.

It’s intriguing to think there are other exotic objects out there, formed as matter is compressed into tighter and tighter configurations, as the different limits of physics are reached and then crossed. Astronomers will keep searching for quark stars, and I’ll let you know if they find them.

See All Five Naked Eye Planets in the Dusk Sky at Once

Solar System

Hosting an evening star party this summer? You’re in for a treat. Starting later this week, all five naked eye planets (Mercury, Venus, Mars, Jupiter and Saturn) are visible in the evening sky at dusk for a brief few weeks. We had a similar lineup in the dawn sky earlier in 2016, as the Earth had all the inner planets in its forward-facing view — now, we see these same planets in our collective rear view mirror, as we lap Mars, Jupiter and Saturn on the inner track, while Mercury and Venus race to catch up with us.

Dusk on the evening of August 8th. Image credit: Stellarium.
Dusk on the evening of August 8th, looking to the southwest. Image credit: Stellarium.

At their narrowest, the planets from Saturn to Mercury fit within a span just 75 degrees wide in the last half of August. A wide field all-sky shot should catch ’em all in the same frame at once. This isn’t a ‘grand conjunction’ in a strict sense. To have all five planets visible, you need the slowest and outermost of the five — Jupiter and Saturn, with orbital periods of 11.9 and 29.5 years respectively — in the same general swath of sky. Both are headed towards conjunction on December 21st, 2020, making such groupings more frequent as they race past the other three. The next true quintuple grand conjunction occurs on September 8th, 2040, when all 5 planets span just 9.3 degrees of the sky… the closest span since September 18th, 1186!

Can you see 'em? Five planets from Monte Mario in Rome on February 2nd, 2016. Image credit: Gianluca Masi/The Virtual Telescope project.
Can you see ’em? Five planets from Monte Mario in Rome on February 2nd, 2016. Image credit: Gianluca Masi/The Virtual Telescope project.

There’s  a lot to watch out for in the next few weeks. Here’s a who’s who of planets this July and August, from east to west:

Saturn: shining at magnitude +0.4 in the constellation Ophiuchus, Saturn is fresh off of opposition on June 3rd. Riding high in the southeast at dawn, Saturn makes a close 4.4 degree pass near Mars on August 24th, and the pair makes a straight line completed by the bright star Antares on the same date.

Mars: High to the south in the constellation Libra at dusk, Mars begins its slow dive into the dusk during the last half of 2016. Currently shining at a respectable magnitude -0.9, Mars passed opposition on May 22nd and is headed towards a grand opposition in 2018, nearly as close as the historic close pass of 2003.

Jupiter: Sitting in the constellation Leo, Jupiter shines at magnitude -1.6 and is about 20-30 degrees above the southwestern horizon at dusk. Jupiter passed quadrature 90 degrees east of the Sun on June 4th and opposition for 2016 on March 8th.

Venus: The bashful planet of the group, Venus is slowly appearing from behind the Sun low in the dusk and headed for a brilliant dusk apparition later in 2016 and early 2017. Currently 3 degrees east of the Sun on July 31st, Venus reaches greatest elongation 47 degrees east of the Sun on January 12th, 2017. We’ve just been able to begin spying Venus using binocs last week from the rooftop of our Casablanca Air BnB. Follow that planet, as Venus makes a close 6′ pass near Jupiter on August 27th.

Mercury: And the innermost planet makes five, as Mercury reaches greatest elongation 27 degrees east of the Sun on August 16th. When can you first catch sight of Mercury, completing the fivesome? Jupiter and Venus actually make great bookends in the hunt, as +0.5 magnitude Mercury wanders between them through early August. It’s too bad dusk twilight obscured the view this past weekend, as both Mercury and Venus photobombed the Beehive Cluster M44 in Cancer. Mercury also passes 20′ from the bright star Regulus on July 30th.

Looking west on the evening of July 19th, 2016. Credit Starry Night Education Software.
Looking west on the evening of July 19th, 2016. Credit Starry Night Education Software.

But wait, there’s more. The Moon passes New on August 2nd, entering back into the dusk sky. The one day old Moon will pass the grouping of Venus, Regulus and Mercury on the evening of August 4th, actually occulting (passing in front of) Mercury for the southernmost tip of South America. The Moon then moves on to occult Jupiter for good measure on August 6th for the South Pacific and southeast Asia in the daytime. Finally, the waxing gibbous Moon makes a wide pass near Mars, Antares and Saturn on the evening of August 12th, on the same evening that the 2016 Perseids are due to occur.

The footprint of the August 4th occultation of Mercury by the Moon. Image credit: Occult 4.2 software.
The footprint of the August 4th occultation of Mercury by the Moon. Image credit: Occult 4.2 software.

The Moon also reaches the nearest apogee (think ‘closest far point’) of the year, at 404,265 kilometers from the Earth on August 10th and reaches Full on August 18th, featuring a subtle penumbral eclipse and the start of eclipse season 2 of 2 for 2016.

More on all of these events in the coming weeks. So, if you find yourself out hunting Pokémon G0 creatures ’til the late dusk hours this summer, don’t forget to look up at the greatest show in the solar system!