The BBC has recently reported on a new interstellar visitor to our solar system. It is thought to be a comet and was discovered by an amateur astronomer.
This makes this one the second uninvited guest to our solar system from outer space in recent years, since 'Oumuamua in 2017.
What do we know about our new interstellar guest?
At the present time, we know very little, but the Minor Planet Center (MPC) at Harvard University has issued a formal announcement about it.
It was initially noticed by an amateur stargazer, Gennady Borisov on the 30th of August this year.
He observed it from the Crimean Astrophysical Observatory in Bakhchysarai.
Let's put a face to an amazing discovery. Gennadii Borisov found what appears to be a large comet that's now swooping into our solar system from interstellar space. https://t.co/L672i9hXG9 pic.twitter.com/Dk9r3gLUm2— Corey S. Powell (@coreyspowell) September 11, 2019
At the time it was about three astronomical units or 450 million km from our Sun.
What has been thus far ascertained is that the stranger appears to have a hyperbolic orbit. This would indicate, according to expert opinion, that it has its origins from well outside our solar system.
Perhaps, as some have claimed, it may have come from a neighboring solar system instead.
Hyperbolic orbits is an eccentric one. This means its shape (if looked from above) would be far from a perfect circle. Its orbit has, according to estimates, an eccentricity of about 3.2. For reference, a perfect circle has an eccentricity of, unsurprisingly, 0, while the elliptical orbits of most planets, asteroids, and comets tend to range between 1 and 0.
It was initially given the designation gb00234 but has now been given the name Comet C/2019 Q4 (Borisov).
Is it another 'Oumuamua?
From what has been discovered so far, the answer to the above question is 'no.'
'Oumuamua discovered on the 19th of October, 2017 was initially classified as a comet, much like our new visitor.
This was because of its similar hyperbolic trajectory but it lacked the tell-tale signs of a coma (or fuzzy envelope around its nucleus).
Comet C/2019 Q4 (Borisov) on the other hand, appears to be a comet.
It has a very clear coma and a well developed, characteristic comet tail.
Also, unlike 'Oumuamua, C/2019 Q4, it is much larger — the former is estimated to be between 100 and 1000 meters long.
Current estimates are that it appears to be around 20 km wide. It is also very bright.
"In addition, 'Oumuamua was also spotted after its closest approach to the Sun (perihelion), so it wasn't visible long enough for astronomers to answer the many questions they had. C/2019 Q4 (Borisov), meanwhile, is still approaching our Solar System and shouldn't reach perihelion until 10 December," the BBC reports.
Its arrival is very exciting for astronomers
Within the official announcement from the MPC, was a call for all astronomers to keep an eye on it. According to the MPC, "absent an unexpected fading or disintegration, [C/2019 Q4] should be observable for at least a year."
Its early sighting should enable astronomers to make exciting observations about it.
Astrophysicist Karl Battams, from the Naval Research Laboratory in Washington DC, tweeted:
Unlike 'Oumuamua, whose asteroid-or-comet nature still gets debated, this one is definitely a comet. If it is unequivocally interstellar, it'll be fascinating to see how its composition (spectral properties) compare to the variety we see in comets from our own solar system.— Karl Battams (@SungrazerComets) September 11, 2019
Another astrophysicist Simon Porter, from the Southwest Research Institute (SwRI) in San Antonio, Texas, also added this on Twitter:
Yes. With such a bright coma, we should be able to get beautiful spectra of Q4 and hopefully measure isotopic ratios (which may be different from in "domestic" comets). https://t.co/uRtMadqZ6V— Simon Porter (@AscendingNode) September 11, 2019