Hello Space Fans and welcome to another edition of Space Fan News.
This week, astronomers have further clarified something that I have long found confusing:
what is the difference between a gas giant planet and a brown dwarf star?
Brown dwarfs are sometimes called failed stars and are among the coldest known free-floating
celestial bodies in the universe, with some astronomers speculating that they may even
be room temperature.
Well a new study out this week show that they're not quite that cool, the objects they looked
at are warmer than previously thought with temperatures about 120 to 150 degrees Celsius
(250-350 degrees Fahrenheit).
To reach such low surface temperatures after cooling for billions of years means that these
objects can only have about 5 to 20 times the mass of Jupiter.
Unlike the Sun, these objects' only source of energy is heat generated from their own
gravitational contraction, and that depends directly on their mass.
Since these objects glow primarily in the infrared, and they are very faint, characterizing
them is a real challenge.
To get accurate temperatures, we need to know how far away they are, and to measure how
far away they are, they use a method called parallax.
Parallax is an apparent shift of something close against the background of something
far away.
To see it, hold your finger out at arms length and alternate closing one eye.
Your finger will appear to shift against the back of the wall.
That's parallax and it only works with things relatively close to us.
The farther away something is, the smaller the shift.
With these objects in this study, they measured the position of a brown dwarf while the Spitzer
Space Telescope was in one spot in its orbit, then again when it was halfway around.
The shift was minuscule, but measurable.
The kind of accuracy required to get a distance that would allow adequate temperature reading,
they needed the same precision as knowing the position of a firefly to within 1 inch
from 200 miles away.
So now we know that these brown dwarfs are pretty warm, warmer than we thought, so they're
more like stars.
You could call them planets as well, but since these objects formed on their own and not
in a protoplanetary disk, most astronomers call them brown dwarf stars, even though they
have the same mass as many gas giant planets.
See?
Crystal Clear Huh?
Next, astronomers using a worldwide network of radio telescopes have found strong evidence
that a powerful jet of material shooting out at nearly light speed by a galaxy's central
black hole is blowing massive amounts of gas out of the galaxy.
These jets are important to understand because all this stuff flying out of the galaxy limits
the growth rate of the central black hole and it slows down the rate of star production
within that galaxy.
Understanding how this process works is key to understanding galaxy development.
Astronomers have long been puzzled because theories suggest that galaxies should be much
bigger than they are and contain more stars.
Observations don't bear that out and these jets may be one reason why.
Another may be violent stellar winds from bursts of star formation, but here we may
be seeing pushback from the jets powered by the central supermassive black hole.
The galaxy they looked at was called 4C12.50, nearly 1.5 billion light-years from Earth.
They chose this galaxy because it is at a stage where the black-hole "engine" that produces
the jets is just turning on.
At the ends of both jets, the researchers found clumps of hydrogen gas moving outward
from the galaxy at 1,000 kilometers per second.
One of the clouds has much as 16,000 times the mass of the Sun, while the other contains
140,000 times the mass of the Sun.
The larger cloud is roughly 160 by 190 light-years in size.
According to the team, this is the most definitive evidence yet for an interaction between the
swift-moving jet of such a galaxy and a dense interstellar gas cloud.
They believe they are seeing in action the process by which an active, central engine
can remove gas --the raw material for star formation -- from a young galaxy.
Now if you'll remember, back in July in SFN 105 I reported that the ALMA team had found
evidence of gas being blown from NGC 253, a much closer galaxy, so it looks like astronomers
are starting to get some good observations to compare their models against.
Finally, astronomers using our old friend the Very Large Telescope have found the oldest
known twin to our Sun.
Located 250 light-years from Earth, the star HIP 102152 is more like the Sun than any other
solar twin — except that it is nearly four billion years older.
Now what's really cool here is that this older, but almost identical star gives us an unprecedented
chance to see how the Sun will look when it gets that old.
They found that HIP 102152 in the constellation of Capricorn is the oldest solar twin known
to date.
It is estimated to be 8.2 billion years old, compared to 4.6 billion years for our own
Sun.
Studying HIP 102152 allows scientists to predict what may happen to our own Sun when it reaches
that age, and they have already made one significant discovery.
It turns out that our sun doesn't have as much lithium in it as it should.
Lithium is the third element in the periodic table and was created in the Big Bang along
with hydrogen and helium.
Astronomers have pondered for years over why some stars appear to have less lithium than
others.
With these new observations of HIP 102152, astronomers have taken a big step towards
solving this mystery by pinning down a strong correlation between a Sun-like star's age
and its lithium content.
The Sun now has just 1% of the lithium content that was present in the material from which
it formed.
Examinations of younger sun-like stars have hinted that these stars contain significantly
larger amounts of lithium, but up to now scientists could not prove a clear correlation between
age and lithium content
According to the lead author on the paper, Dr. Talawanda Monroe, "We have found that
HIP 102152 has very low levels of lithium.
This demonstrates clearly for the first time that older solar twins do indeed have less
lithium than our own Sun or younger solar twins.
We can now be certain that stars somehow destroy their lithium as they age, and that the Sun's
lithium content appears to be normal for its age."
Well that's it for this week Space Fans, thank you for watching and as always, Keep Looking
Up!