Hello Space Fans and welcome to another edition of Space Fan News. This week, astronomers think they’ve found a stray black hole roaming through our galaxy which promises to help us find many more of these hidden objects; water molecules have been detected in the atmosphere of the Hot Jupiter exoplanet known as 51 Pegasi b; and I have updates on NASA’s Cassini and Juno missions.
Everybody knows that black holes are hard to see and that’s because they emit no light of their own. The only way to really see a black hole is by watching what it does as it devours everything around it. If nothing happens to be around it, then for all intents and purposes, it’s invisible to us.
Astronomers estimate that there are between 100 million and 1 billion black holes in our Milky Way Galaxy. The reason there is such a huge spread in the error bars there has to do with the fact that we really don’t have an accurate census of these things because, well, they’re black and most of the black holes we know about, we know about because they are eating a star or a gas cloud and in turn radiating high energy electromagnetic waves that we can see with our X-ray and gamma-ray telescopes.
Even with those so-called active black holes - the ones eating everything around it - we still don’ see them all because the orientation may not be right for us to detect them. What we really need is some way to find all black holes regardless of if they are active or not.
Well there may be hope because this week astronomers think they have found a stray black hole that’s blasting through a huge gas cloud disturbing the gas in in a way that resembles a bullet flying through water.
Astronomers using radio telescopes in Chile and Japan were observing molecular clouds around the supernova remnant known as W44 and is located 10,000 light-years away from us. Their primary goal was to examine how much energy was transferred from the supernova explosion to the surrounding molecular gas, but they happened to find signs of a hidden black hole at the edge of W44.
During the survey, the team found a compact molecular cloud with a very strange motion. This cloud, which they’re calling the "Bullet," has a speed of more than 100 km/s, and that exceeds the sound speed in interstellar space by more than two orders of magnitude. In addition, this cloud, with the size of two light-years, moves backward against the rotation of the Milky Way Galaxy.
To investigate the origin of the Bullet anomaly, the team performed intensive observations of the gas cloud with Atacama Submillimeter Telescope Experiment (ASTE) and the Nobeyama 45-m Radio Telescope. The data indicate that the Bullet seems to jump out from the edge of the W44 supernova remnant with immense kinetic energy. The astronomers are saying that most of the Bullet has an expanding motion with a speed of 50 km/s, but the tip of the Bullet has a speed of 120 km/s. This kinetic energy is a few tens of times larger than that injected by the W44 supernova. It seems impossible to generate such an energetic cloud under ordinary environments.
So what gives? Well they have two possible explanations for what may be going on here. One scenario is that they’re calling the "explosion model" where an expanding gas shell of the supernova remnant passes by a static black hole. The black hole then pulls the gas very close to it, giving rise to an explosion, which accelerates the gas toward us after the gas shell has passed the black hole.
If that’s happening then the size of the black hole is estimated to be about three and a half solar masses.
The other idea is that it’s the black hole itself which is moving very, very fast through the gas cloud and coming out the other side dragging gas behind it in a long stream. If that’s what’s going on then the black hole is probably closer to ten times larger than the previous scenario at 36 solar masses.
From this data though, it’s hard to tell which scenario is playing out. What they need are higher resolution images of the gas cloud from the Atacama Large Millimeter/submillimeter Array (ALMA).
But regardless of which scenario is in play here, we have one more tool in the toolkit to try and detect these lone black holes stalking the Milky Way.
Next, because of a fortuitous alignment of the exoplanet known as 51 Pegasi b, astronomers were able to detect the presence of water molecules in the atmosphere of this hot Jupiter exoplanet.
Located some 50 light years away, 51 Pegasi b is the first exoplanet discovered orbiting a main-sequence star and the first known hot Jupiter. It is called a hot Jupiter because it has orbital period of less than 10 days (4.23 days) and is similar in characteristics to the solar system's biggest planet, with a mass of about 0.47 Jupiter masses. It also has high surface temperature, as it orbits its parent star 51 Pegasi very closely—at a distance of about 0.05 AU.
Right now, astronomers can only detect what’s in the atmosphere of an exoplanet if it happens to pass between Earth and the star it’s orbiting. By looking at the spectrum through spectrographs and noting where the absorption lines are, astronomers can tell what molecules are in there.
This week a team of astronomers have observed 51 Pegasi and its planet with the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) at the Very Large Telescope (VLT) in Chile. They obtained a total of 42 spectra allowing them to observe the radial-velocity shift of the water features in the planet's day side atmosphere.
With those instruments, astronomers have directly detected water molecules in the spectrum of the exoplanet’s atmosphere.
Besides water, the researchers also searched for molecular features that may come about from the expected major carbon- and oxygen-bearing gases at the observed wavelengths, like water carbon dioxide and methane.
You know, in case there might be life there too.
But sadly, they found no significant signal from those molecules that would indicate their presence at the abundances probed by their model grid in the atmosphere of 51 Pegasi b.
It was a long shot after all, I mean, this is a hot Jupiter for goodness sake.
One other thing these spectra were able to tell us, the team also noted that an upper limit to the rotational velocity of 51 Pegasi b should be less than 5.8 km s-1 - it shouldn’t be rotating any faster than that according the the shifts in the spectra. However, instruments with higher resolution are going to be needed to confirm if the planet's rotation is tidally locked to its host star.
Finally, NASA says there is no groundhog day on Jupiter. This strange pronouncement came as they said that the Juno probe sas just completed another close flyby of the Jovian planet. This was Juno’s fourth close flyby and they are still getting the data back from the spacecraft as we speak.
Also the JunoCam I told you about was also operating and taking pics of all the points of interest you guys voted on before voting closed and it looks like many of the images from perijove three are already being processed by member of the public. So thanks for voting and get in there and start processing those images.
In a related story this week, the Cassini spacecraft, which I told you in SFN #190 was going to get really close to Saturn before plunging to its death later this year, has started returning some of the closest images of the rings we’ve ever seen.
Cassini is now in it’s ‘ring-grazing’ orbit phase and providing viewpoints and a level of detail we havent seen since Cassini first arrived at Saturn in 2004
Here is a region in Saturn's outer B ring. NASA's Cassini spacecraft viewed this area at a level of detail twice as high as it had ever been observed before.
This image shows a region in Saturn's outer B ring. And from this view, it is clear that there are still finer details to uncover.
Here is a region in Saturn's A ring. Here we can see many small, bright blemishes due to cosmic rays and charged particle radiation near the planet.
And this Cassini image features a density wave in Saturn's A ring (at left) that lies around 134,500 km from Saturn. Density waves are accumulations of particles at certain distances from the planet. This feature is filled with clumpy perturbations, which researchers are informally referring to as "straw."
For now, the veteran spacecraft is shooting past the outer edges of the rings every week, gathering some of its best images of the rings and moons. But as I’ve told you before, things change in late April when Cassini will begin the first of its 22 final orbits, with each one passing between the rings and Saturn itself.
I’ll keep you posted.
Well, that is it for this week Space Fans, thanks to this week’s sponsor .SPACE domains, the place to go to get a cool domain name for all of us space nerds. Thanks also to SFN Patreon Patrons whose support each month really keeps the lights on at SFN Headquarters, thanks to all of you for watching and as always, Keep Looking Up!