V471 Tauri is a binary star system in the Hyades cluster in the constellation Taurus.  It is estimated to be around 600 million years olds and 163 light-years from Earth.

At one time, the larger of the two stars expanded to become a red giant shedding its gases.  These gases eventually disperse as the red giant shrinks down to a white dwarf.  The white dwarf and the normal star now move close together.  This is common in the life of binary stars where the two stars are about the same size as our sun.  They are known as post-common-envelope binaries.

The two stars in V471 Tauri orbit each other once every 12 hours.  Twice per orbit, as observed from Earth, one star passes in front of the other.  At this time, as one star eclipses the other, instruments on Earth can measure the change in brightness.  Scientists have been using the ULTRACAM system on ESO's New Technology Telescope in Chile to measure V471 Tauri with an accuracy of better than two seconds.  They discovered that the times varied from pass to pass.  This was explained by the theorized existence of a brown dwarf.  A brown dwarf is a star that failed to ignite.

To find the brown dwarf, scientists used the SPHERE instrument on the Very Large Telescope.  SPHERE is able to image a brown dwarf that is 70,000 times fainter and only 0.26 arcseconds from a star.  The brown dwarf theorized to be around V471 Tauri would be much larger than that.  But SPHERE found nothing.  No brown dwarf.  No companion star.  Nothing.

The missing brown dwarf means that the current explanation of the the variable brightness is wrong.  Not only does this invalidate the theory at V471 Tauri, but puts in doubt like-theories at other stars.

New theories are being proposed.  It may be possible that magnetic field variations in the larger star is the cause.  This effect is called the Applegate mechanism.  As the magnetic field produces changes in the shape of the star, the apparent brightness of the star will change as seen from Earth.

NGC2276-3c is a newly discovered cosmic object.  It is located in the arm of the spiral galaxy NGC 2276, located 100 million light years away.  Astronomers think it could be an intermediate-mass black hole (IMBH).

Astronomers have gathered a lot of information about supermassive black holes (millions to billions times the mass of the sun) and small black holes (five to thirty times the mass of the sun).  But they have not been able to find middle sized black holes (a few hundred to a few thousand times the mass of the sun) although they have been theorized.  They may even be the seeds from which the supermassive black holes form.

A new study used the Chandra X-ray space telescope and the European Very Long Baseline Interferometry (VLBI) Network to study NGC2276-3c.  NGC2276-3c had been known as a ultraluminous X-ray source.  Astronomers used both instruments at the same time to take their measurements.  They discovered a mass of about 50,000 times that of the sun.  That puts it in the range for a IMBH.

It was discovered that NGC2276-3c has a powerful radio jet that extends up to 2000 light-years.  In the first 1000 light-years of the jet there was observed no young stars.  This suggests the IMBH could have cleared out that area of space and suppressed the formation of new stars.

Another question raised is where did this IMBH come from?  It is located in the arm of the spiral galaxy NGC 2276.  Was it formed in the galaxy or did it come from the center of a dwarf galaxy that collided with it and merged with it in the past?

Further studies of NGC2276-3c can help provide insight into the origins of the supermassive black holes and their effects on the early universe.  Finding an IMBH can now finally put the missing part of the black hole family tree together.