NASA's Voyager 2 becomes second spacecraft to reach interstellar space
Washington: More than four decades after beginning its epic journey, NASA's Voyager 2 spacecraft has crossed the elusive boundary that marks the edge of the Sun's realm and the start of interstellar space, scientists have announced.
According to the researchers at the University of Iowa in the US, Voyager 2 has entered the interstellar medium (ISM), the region of space outside the bubble-shaped boundary produced by wind streaming outward from the Sun.
This makes Voyager 2 the second human-made object to journey out of the Sun's influence, following the US space agency's Voyager 1's solar exit in 2012.
The study, published in the journal Nature Astronomy, confirmed Voyager 2's passage on November 5, 2018, into the ISM by noting a definitive jump in plasma density detected by a plasma wave instrument on the spacecraft.
The marked increase in plasma density is evidence of Voyager 2 journeying from the hot, lower-density plasma characteristic of the solar wind to the cool, higher-density plasma of interstellar space, the researchers said.
It is also similar to the plasma density jump experienced by Voyager 1 when it crossed into interstellar space, they said.
"In a historical sense, the old idea that the solar wind will just be gradually whittled away as you go further into interstellar space is simply not true," said Professor Don Gurnett from the University of Iowa, and corresponding author on the study.
"We show with Voyager 2 -- and previously with Voyager 1 -- that there's a distinct boundary out there. It's just astonishing how fluids, including plasmas, form boundaries," Gurnett said.
Voyager 2's entry into the ISM occurred at 119.7 astronomical units (AU), or more than 11 billion miles from the Sun. Voyager 1 passed into the ISM at 122.6 AU.
The spacecraft were launched within weeks of each other by NASA in 1977, with different mission goals and trajectories through space. Yet they crossed into the ISM at basically the same distances from the Sun.
That gives valuable clues to the structure of the heliosphere -- the bubble, shaped much like a wind sock, created by the Sun's wind as it extends to the boundary of the solar system, the researchers said.
"It implies that the heliosphere is symmetric, at least at the two points where the Voyager spacecraft crossed," said Bill Kurth, University of Iowa research scientist and a co-author on the study.
"That says that these two points on the surface are almost at the same distance," Kurth said. "There's almost a spherical front to this. It's like a blunt bullet," Gurnett added.
Data from the instrument on Voyager 2 also gives additional clues to the thickness of the heliosheath, the outer region of the heliosphere and the point where the solar wind piles up against the approaching wind in interstellar space, which Gurnett likens to the effect of a snowplow on a city street.
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I'm 100 per cent ready to play T20I World Cup: Dinesh Karthik
Kolkata, Apr 20: Veteran wicketkeeper-batter Dinesh Karthik, who has been in phenomenal form in this IPL, has not given up on his dream to play for India again and would do "everything he can to be in that flight" to the T20 World Cup in the USA and West Indies next month.
Karthik, who will turn 39 by the time the World Cup kickstarts on June 1, was also part of the last edition of the T20I World Cup in Australia in 2022, which was also his last appearance for Team India.
Since then he has become an off-the-field cricket expert, involved in commentary stints.
Returning to IPL this season, he has taken his batting to a new level and displayed some astonishing power-hitting to strike at a rate of 205-plus.
He is also the third leading run-getter for RCB with 226 runs, behind Virat Kohli (361) and skipper Faf du Plessis (232).
"At this stage in my life, it would be the greatest feeling for me to represent India. I'm very, very keen to do so. There is nothing bigger in my life other than representing India in this T20 World Cup," the RCB wicketkeeper-batters said ahead of clash against KKR .
With Karthik's also emerging as a contender, the wicketkeeper slot will be a hotly-contested one for which the Team India think tank may pick two at the most.
Making a comeback from a near-fatal accident, Rishabh Pant has also showed positive intent while captaining Delhi Capitals, and Sanju Samson (Rajasthan Royals), Ishan Kishan (Mumbai Indians), KL Rahul (Lucknow Super Giants) are also in the fray.
Karthik said he would respect whatever the Big Three -- coach Rahul Dravid, captain Rohit Sharma and chairman of selectors Ajit Agarkar -- decide.
"I also feel there are three very, very stable, honest people who are at the helm to decide what should be the best Indian team for the World Cup -- Rahul Dravid, Rohit Sharma and Ajit Agarkar.
"And I'm completely with them. I respect any decision that they take. But all I can say is I'm 100 per cent ready, and I'll do everything I can to be on that flight to the World Cup."
'I'm no Russell or Pollard'
Karthik further emphasised the importance of understanding his strengths as a player, focusing on precision rather than power-hitting like an Andre Russell or Kieron Pollard.
He said he analyses bowlers' patterns to strategise his shots, visualising scenarios during practice to enhance his batting repertoire.
"These days as a player, you need to understand your strengths. I'm not a Russell or a Pollard who can just mishit a ball and get a six for it, rather," said Karthik.
The other day Karthik smashed seven sixes and five fours in his 35-ball 83 in pursuit of a record 288 but eventually RCB fell short by just 25 runs.
"So, I need to understand how I can beat gaps, what sort of balls I can hit for boundaries. And I realised there was a certain pattern in which bowlers were bowling to me, so I needed to try and work out a solution for that.
"Hence, when I practice, I try and understand, okay, if this is what they're going to bowl at me, how am I going to get a boundary, visualising a field that is going to be in place for me.
"So, I worked like that, and I worked backwards, and that helped me, you know, really learn a couple of shots more, at the back end. It's been great to go out there and express myself, and it's been thoroughly enjoyable to do what I'm doing for RCB as a finisher," he added.
